xi ELECTRICAL FISHES 463 



fishes, considerable magnitudes of E.M.F. which, as du Bois- 

 Eeymond himself pointed out, cannot be explained on Boll's 

 hypothesis, owing to the very marked short-circuiting that exists 

 under all circumstances between the individual nerve-endings. 

 In Malapterurus, however, where one axis -cylinder is alone 

 correlated with each plate, each axis -cylinder would, as du Bois- 

 Keymond remarks, under even the most favourable conditions 

 (such as " that the point of junction should contain a cross-section 

 of the nerve with the parelectronomic layer, and that, as appears 

 hardly possible, this cross-section should be a superficial element 

 at right angles to the direction of activity in the organ), be 

 embedded separately in the mass of the plates, whereby such a 

 diminution of its external action would result, that there could 

 no longer be any question of explaining the discharge of Malapte- 

 rurus by the variation of the electrical nerve-endings. Du 

 Bois-Eeymond further points out that on Boll's theory the 

 existence of the electrical plates (often of such a complex structure) 

 would have no significance in the electrical organ, and would be 

 inexplicable. 



As we have said, it was du Bois-Eeymond who first, in 1843, 

 expressed his conviction that it was the latter (the so-called 

 " gelatinous discs ") which " at the moment of discharge become 

 electromotive in a given direction, under the influence of a nervous 

 agency stimulated by whatever means," and which multiply 

 their action after the manner of the voltaic pile. It would thus 

 not be the negative variation of the nerve current that pro- 

 duced the discharge, but a process in the electrical plates trans- 

 formed from muscles, comparable with the negative variation of the 

 muscle current, as set forth from the standpoint of the pre-existence 

 theory. Du Bois-Eeymond (supra] would accordingly represent 

 each plate as containing countless dipolar electromotive mole- 

 cules, " able during rest to turn their poles either in all possible 

 or in two opposite directions, so that the external action 

 neutralises itself, while during discharge the poles are turned 

 rapidly and collectively toward the surface of the organ, whence 

 proceeds the positive current." Du Bois-Eeymond reckons as 

 one of the main supports of this theory the dictum derived from 

 Delle Chiaje's and Babuchin's doctrine of the preformation of the 

 electrical elements, that the E.M.F. of the discharge must increase 

 proportionately with the diameter of the plates. Since the E.M.F. 



